1. Field of the Invention
This invention relates generally to projectiles and more particularly to rifled bullets for use in smooth bore gun barrels.
2. Description of the Prior Art
There has been an increased interest in recent years in the use of slugs especially for the hunting of large game animals. Conventional slugs known in the art tend to consist of a solid mass of lead with a relatively blunt nose and generally cylindrical body. These solid lead slugs were optionally equipped with helical ribbing disposed about the outer periphery of the slug. The incorporation of the helical ribbing (rifling) imparts a spin to the projectile while in flight and creates a generally more aerodynamic slug. However, many hunters have complained that even with the outer rifling these solid lead slugs were inaccurate, had a short effective range and lacked knockdown power. Furthermore, these rifled slugs could not be utilized in a traditional smooth bore barrel shotgun as they would cause undue wear and leading to the inner barrel surface and accuracy and gyration would both be significantly impaired.
Attempts have been made to overcome these problems of the prior art by manufacturing projectiles from lighter weight materials or alternately providing a hollow center passage through the projectile such as to form a tubular shape. The tubular projectile has especially proven to possess certain advantages over previous projectile designs as the tubular passage significantly reduces ballistic drag and shock wave and increases impact force and target penetration. The tubular projectile can optionally be provided with the outer helical rifling to impart a gyration on the airborne projectile. Variations in the size and shape of the hollow center passage have been demonstrated such as expanding the size of the inlet area aperture and providing thicker passage walls with varying success rates. It has been therefore concluded that minor changes of contour can make a decisive difference in the success or failure of the design in terms of its ballistic and aerodynamic characteristics. A particularly desirable design has proven to consist of a hollow passage wherein the inner surface gradually tapers inwardly converging toward a throat section immediately followed by a divergent aft section. The incorporation of the throat section has been shown to optimize many of the critical ballistic characteristics. However, when rifling is included on the exterior surface of this throated slug, its use in smooth bore shotguns is questionable.
A longfelt need has therefore existed in the prior art for the development of an extremely accurate tubular slug for use in a smooth bore barrel shotgun which still intrinsically spins during flight producing gyroscopic stabilization.